1 PROJECT SUMMARY/ABSTRACT 2 This research program?s broad, long-term objective is to improve health outcomes for patients suffering from 3 acute ischemic stroke (AIS) resulting from large vessel occlusions. We will achieve this purpose by developing 4 improved access tools for stroke intervention procedures, which specifically target tool innovations that provide 5 support for embolectomy devices and arrest flow during the procedure. Based on multiple landmark 6 randomized trials in 2015, urgent embolectomy has displaced IV-tPA as a standard of care. Large clinical 7 studies have documented that the use of proximal occlusion balloons, which stop antegrade flow while 8 retrieving the culprit embolus allowing aspiration of clot remnants, have numerous beneficial effects that 9 include quicker procedures, improved rates of recanalization, and improved clinical outcomes as compared to 10 procedures done without such flow arrest. In current practice, such balloons are used in only 50-60% of 11 procedures due to substantial shortcomings. For example, they require very large access sheaths, yet their 12 usable lumens are relatively small. Furthermore, they provide poor support for distal access devices. We will 13 design and develop improved balloon occlusion devices that overcome all shortcomings noted with current 14 tools, thereby providing the community with highly stable balloon devices with lumens large enough to accept 15 even the largest distal access tools, while using smaller arteriotomies to diminish access site bleeding risk. If 16 successful, our novel Balloon Occlusion Sheath for Stroke (BOSS) development program will lead to markedly 17 enhanced market penetration for the use of balloon occlusion maneuvers with resultant improvement in clinical 18 outcomes.